<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .nav{
            list-style: none;
        }
    </style>
</head>
<body>
    <ul class="nav">
        <li>榴莲</li>
        <li>臭豆腐</li>
        <li>鲱鱼罐头</li>
        <li>大猪蹄子</li>
    </ul>
    <script>
        //打印所有的小li
        var lis = document.querySelectorAll('li');
        for(var i = 0; i < lis.length; i++){
            (function(i){
                setTimeout(function(){
                console.log(lis[i].innerHTML);
            },3000)
            })(i)
        }
    </script>
</body>
</html>